R Shiny Interactive plot title for ggplot - r

Question

I am trying to create Shiny App which is able to display interactive plot title (dependent on the choosen value for x axis)
Very simple example:
library(shiny)
library(DT)
library(ggplot2)
x <- as.numeric(1:1000000)
y <- as.numeric(1:1000000)
z <- as.numeric(1:1000000)
data <- data.frame(x,y, z)
shinyApp(
ui = fluidPage(selectInput(inputId = "yaxis",
label = "Y-axis",
choices = list("x","y","z"),
selected = c("x")),
dataTableOutput('tableId'),
plotOutput('plot1')),
server = function(input, output) {
output$tableId = renderDataTable({
datatable(data, options = list(pageLength = 10, lengthMenu=c(10,20,30)))
})
output$plot1 = renderPlot({
filtered_data <- data[input$tableId_rows_all, ]
ggplot(data=filtered_data, aes_string(x="x",y=input$yaxis)) + geom_line()
})
}
)
I have tried this code:
ggtitle("Line plot of x vs",input$yaxis)
It was not working, plot has not been displayed, giving me an Error:
Warning: Error in ggtitle: unused argument (input$yaxis)
[IMPORTANT]
using ggtitle(input$yaxis) gives me an interactive title, however i need to build up a sentence (like: Line plot of x vs input$yaxis), in which the reactive argument (input$yaxis) is a part of it!
Thanks for any help!
Cheers

Answer 1

Change:
ggtitle("Line plot of x vs",input$yaxis)
To
ggtitle(paste("Line plot of x vs",input$yaxis))
As the error suggests, you have too many arguments passed to the ggtitle function, paste will create a single character out of your two inputs, with a space in between. You can vary the separation between the two with sep =.